Unlocking the Power of strtoull(): A Comprehensive Guide
What is strtoull()?
The strtoull() function in C++ is a powerful tool that interprets the contents of a string as an integral number of a specified base and returns its value as an unsigned long long int. But that’s not all – it also sets a pointer to point to the first character after the last valid character of the string, or null if there isn’t one.
How Does it Work?
The strtoull() function takes three parameters: a string, a pointer to a character, and an integer value representing the base. It then interprets the content of the string as an integral number of the given base and returns an unsigned long long int value.
Breaking Down the Parameters
- str: A string having the representation of an integral number.
- end: A reference to an already allocated object of type char*. The value of end is set by the function to the next character in str after the last valid character. This parameter can also be a null pointer, in which case it is not used.
- base: The base of the integral value. The set of valid values for base is {0, 2, 3, …, 35, 36}.
Return Value
The strtoull() function returns either an unsigned long long int value (which is converted from the string) or 0 if no valid conversion could be performed.
Examples Galore!
Let’s dive into some examples to see how strtoull() works its magic.
Example 1: The Basics
When you run the program, the output will be a valid integer value. But what makes up a valid integer value for strtoull()? It consists of:
- An optional + or – sign.
- A prefix 0 for octal base (applies only when base = 8 or 0).
- A prefix 0x or 0X for hexadecimal base (applies only when base = 16 or 0).
- A sequence of digits and/or alphabets (if base is greater than 10).
Example 2: Bases, Bases, Everywhere!
When you run the program, the output will be a demonstration of how strtoull() works with different bases. The valid values for parameter base is {0, 2, 3,…, 35, 36}. A set of valid digits for base 2 is {0, 1}, for base 3 is {0, 1, 2} and so on.
Example 3: Leading Whitespace, Minus, and Invalid Conversion
When you run the program, the output will show how strtoull() handles leading whitespace characters, minus signs, and invalid conversions.
Example 4: The Base 0 Conundrum
When you run the program, the output will demonstrate how strtoull() works when the base is 0. In this case, the numeric base is determined automatically by looking at the format of the string.
By now, you should have a solid understanding of how strtoull() works and how to harness its power in your C++ programs. Happy coding!